This invention relates generally to fuel cells and, more particularly, to fluid flow plate configuration.
Fuel cells electrochemically convert fuels and oxidants to electricity. A Proton Exchange Membrane (hereinafterxe2x80x9cPEMxe2x80x9d) fuel cell converts the chemical energy of fuels such as hydrogen and oxidants such as air/oxygen directly into electrical energy. The PEM is a solid polymer electrolyte that permits the passage of protons (i.e., H+ ions) from the xe2x80x9canodexe2x80x9d side of a fuel cell to the xe2x80x9ccathodexe2x80x9d side of the fuel cell while preventing passage therethrough of reactant fluids (e.g., hydrogen and air/oxygen gases). The direction, from anode to cathode, of flow of protons serves as the basis for labeling an xe2x80x9canodexe2x80x9d side and a xe2x80x9ccathodexe2x80x9d side of every layer in the fuel cell, and in the fuel cell assembly or stack.
In general, an individual PEM-type fuel cell may have multiple, generally transversely extending layers assembled in a longitudinal direction. In a typical fuel cell assembly or stack, all layers which extend to the periphery of the fuel cells have holes therethrough for alignment and formation of fluid manifolds that generally service fluids for the stack. Typically, gaskets seal these holes and cooperate with the longitudinal extents of the layers for completion of the fluid supply manifolds. As is known in the art, some of the fluid supply manifolds distribute fuel (e.g., hydrogen) and oxidant (e.g., air/oxygen) to, and remove unused fuel and oxidant as well as product water from, fluid flow plates which serve as flow field plates of each fuel cell. Other fluid supply manifolds may circulate coolant (e.g., water) for cooling the fuel cell.
Typically, the distribution of reactant gases to the various fluid flow plates in the fuel cell stack, as well as removal of unused reactant gases and water from the plates, is accomplished by the fluid flow manifolds. Each of the various components in the stack has a xe2x80x9cmanifold holexe2x80x9d which, when aligned, form columns that are used as fluid flow manifolds. The fluid flow manifolds conduct their respective fluids substantially perpendicular to the planes of the various fluid flow plates. If a particular plate distributes the fluid that is being conducted through a particular fluid manifold, that manifold must be in communication with that plate""s flow channels.
As can be seen in FIG. 1, in the prior art dive through holes have been used to fluidly connect fluid flow manifolds with their respective flow channels. Fluid flow plate 1 has a plurality of fluid flow manifolds 2, and a plurality of active area flow channels 3 located on each side of the fluid flow plate. In this example, the active area flow channels (not shown) on the opposite side of fluid flow plate 1, are connected to fluid flow manifolds 2, by use of dive through holes 4 and inlet channels 6. Similarly, flow channels 3 are connected to fluid flow manifolds 2 by the use of dive through holes 7 and inlet channels (not shown located on the opposite side of fluid flow plate 1. The dive through holes extend through fluid flow plate 1 thereby allowing fluid from the fluid flow manifolds to enter the flow channels. The use of dive through holes, creates a smooth surface 8 on the fluid face plate thereby allowing a gasket 5 to aid in the sealing of one plate to another. Gasket 5 also aids in sealing the respective fluid manifolds, thereby preventing leaking of fluid.
In such a system the gasket needs to be reversed when applied to the opposite side of fluid flow plate 1. During compression, this can result in uneven loads on the fluid flow plate which may increase the structural requirements of the fluid flow plate. Also when it is desired to use varying types of fluid flow plates, with varying configurations of flow channels fluidly connected to different fluid manifolds, various fluid flow plates must be provided. Various fluid flow plates must be separately provided, and may thus increase the overall cost of the fuel cell assembly.
Accordingly, it is desirable to provide a fluid flow plate which allows fluids to pass from the fluid manifolds directly to the flow channels without creating uneven loads on the fluid flow plates when assembled, and still providing an adequate seal.
The present invention provides, in a first aspect, a fuel cell fluid flow plate having a face and a fluid opening for receiving a fluid. The fluid flow plate has at least one flow channel in its face for distributing a fluid in the fuel cell, a first groove defined within the face to receive a sealing member, and a bridge piece having a first surface and a second surface. The first surface of the bridge piece has at least one channel for fluidly connecting the fluid opening to the at least one flow channel. The second surface of the bridge piece having a second groove defined therein to receive the sealing member.
The present invention provides, in a second aspect, a bridge piece for use with a fuel cell fluid flow plate. The fuel cell fluid flow plate has a face and a fluid opening for receiving a fluid, at least one flow channel in the face for distributing a fluid in a fuel cell, and a first groove defined within the face, the groove adapted to receive a sealing member. The bridge piece comprises a body having a first surface and a second surface. The first surface has at least one channel for fluidly connecting the fluid opening to the at least one flow channel. The second surface has a second groove defined therein to receive the sealing member.
The present invention provides, in a third aspect, a method for forming a fuel cell fluid flow plate assembly, which includes, providing a fluid flow plate having a face and a fluid opening for receiving a fluid. The fluid flow plate has at least one flow channel in the face for distributing a fluid in a fuel cell, and a first groove adapted to receive a sealing member, defined within the face. A bridge piece is provided, having a first surface and a second surface. The first surface has at least one channel, and the second surface has a second groove, adapted to receive a sealing member, defined therein. The bridge piece is placed relative to the fluid flow plate such that the at least one channel of the bridge piece fluidly connects the fluid opening to the at least one flow channel.